McKinley Jessica L, Beran Gregory J O
Department of Chemistry, University of California, Riverside, California 92521, USA.
Faraday Discuss. 2018 Oct 26;211(0):181-207. doi: 10.1039/c8fd00048d.
Quasi-harmonic approaches provide an economical route to modeling the temperature dependence of molecular crystal structures and properties. Several studies have demonstrated good performance of these models, at least for rigid molecules, when using fragment-based approaches with correlated wavefunction techniques. Many others have found success employing dispersion-corrected density functional theory (DFT). Here, a hierarchy of models in which the energies, geometries, and phonons are computed either with correlated methods or DFT are examined to identify which combinations produce useful predictions for properties such as the molar volume, enthalpy, and entropy as a function of temperature. The results demonstrate that refining DFT geometries and phonons with single-point energies based on dispersion-corrected second-order Møller-Plesset perturbation theory can provide clear improvements in the molar volumes and enthalpies compared to those obtained from DFT alone. Predicted entropies, which are governed by vibrational contributions, benefit less clearly from the hybrid schemes. Using these hybrid techniques, the room-temperature thermochemistry of acetaminophen (paracetamol) is predicted to address the discrepancy between two experimental sublimation enthalpy measurements.
准谐近似方法为模拟分子晶体结构和性质的温度依赖性提供了一条经济的途径。几项研究表明，当使用基于片段的方法与相关波函数技术时，这些模型至少对刚性分子具有良好的性能。许多其他研究发现采用色散校正密度泛函理论（DFT）取得了成功。在此，研究了一个模型层次结构，其中能量、几何结构和声子是用相关方法或DFT计算的，以确定哪些组合能对诸如摩尔体积、焓和熵等作为温度函数的性质产生有用的预测。结果表明，与仅从DFT获得的结果相比，基于色散校正的二阶莫勒-普莱斯特定则微扰理论用单点能量细化DFT几何结构和声子，可以在摩尔体积和焓方面提供明显的改进。由振动贡献决定的预测熵，从混合方案中得到的益处不太明显。使用这些混合技术，预测了对乙酰氨基酚（扑热息痛）的室温热化学性质，以解决两个实验升华焓测量值之间的差异。
